1. Field of Invention
The invention relates to roof covering elements and methods for their manufacturing and more particularly to roof covering elements comprising a plurality of plastic stalks being arranged approximately parallel adjacent to each other, their upper ends being joined together by heat bonding, the stalks having irregular lengths and being shaped irregularly at their free ends and having a helical cross-section. Such roof covering elements are used for building roofs to resemble natural thatched roofs.
2. Description of the Prior Art
A roof covering element is known from the German Patent Specification 20 53 642, which comprises a plurality of plastic stalks, arranged approximately side by side and above each other in parallel, being flattened and heat bonded with each other in their upper regions and also heat bonded to an underlying base. It is a disadvantage that the base is a solid plastic sheet which makes the roof covering element stilt, heavy and expensive.
A plastic stalk is known from the German Patent Specification 33 11 366, which is to be used in the same manner as natural stalks, i.e. a plurality of plastic stalks is tied up in bundles and fastened to a conventional roof structure.
This method requires high labour costs, and the roof is sensitive against wind pressure resulting in fractures of the stalks and damages to the roof.
A building element for covering outside walls and roofs for thermal and water protection is known from the German Patent Specification 32 08 460, which comprises stalks and the like material woven into or otherwise fastened onto a carrier fabric, shaped like a grid. This element disadvantageously is sensitive and subject to reduced durability.
Another roof covering element is known from the British Patent Specification 2 039 822, comprising a plurality of plastic stalks being bonded in a carrier base of synthetic resin at their upper regions. The stalks have different lengths. This roof covering element requires a high amount of material and labour costs when producing it and has a high weight per area, which disadvantageously restricts its range of application.
Finally a roof covering element is known from the European Patent Specification 0 202 518 which consists of a plurality of plastic stalks which are arranged approximately parallel adjacent to each other and one above the other, which are flattened in their upper end region and are joined together by heat bonding, the roof covering element having an underlying base which consists of a grid-shaped woven material and is joined to the stalks, likewise by heat bonding, wherein the stalks consist of hard PVC or shock-resistant hard PVC, the stalks are of irregular lengths and are irregularly shaped at their free ends, the stalks have a helical cross-section and the stalks have on their outsides at least one longitudinally extending, projecting web or fluke.
Although the roof covering element described last has advantages in general, it has also be found, that there still is room for improvement regarding the fastening of the ends of the stalks to the grid shaped material, which method requires some effort, and the forming of the stalks having longitudinal webs which finally results in plastic stalks having somewhat different shape than natural stalks.
It is therefore an object of the present invention to provide a roof covering element comprising a plurality of plastic stalks being arranged approximately parallel adjacent to each other and one above the other, being joined together by heat bonding, the stalks having a irregular length and being irregularly shaped at their free ends and having a helical cross-section which roof covering element is light in weight, easy to manufacture and durable in use.
It is also an object of the present invention to provide a plastic stalk for that roof covering element, which is easy to manufacture, durable and resembles a natural stalk.
It is a further object of the present invention to provide a method for producing the plastic stalk according to the invention in a reliable and efficient process.
It is a still further object of the present invention to provide a method for producing the roof covering element according to the invention in a simple and inexpensive process using conventional equipment.
Other objects, advantages, and applications of the present invention will become apparent to those skilled in the art when the accompanying description of a preferred embodiment is read in conjunction with the accompanying drawing.